At a minimum, a lawful arrest requires probable cause. Probable cause generally means that a law enforcement officer has a subjective belief that a crime has been committed, therefore making someone subject to arrest. The officer’s belief must be objectively reasonable as determined later by a judge.
When an officer can make an arrest differs slightly depending on whether the crime a person committed is a felony, (a crime punishable by more than one year in prison), or a misdemeanor, (a crime punishable by up to, but no more than, one year in prison). A law enforcement officer may arrest someone for a felony if the officer believes there is probable cause. In contrast, a law enforcement officer may arrest someone for a misdemeanor if the officer believes a misdemeanor crime has been committed in the officer’s presence.
It should be noted that an arrest is different from what is known as an investigatory stop or detention. An investigatory stop occurs when an officer briefly detains someone for some limited purpose. The most well known example of this sort of detention occurs when a police officer pulls a motorist over for a traffic violation. However, stops may also occur in any number of situations. An investigatory stop is only legal if an officer has a reasonable suspicion that a crime or violation has occurred. Reasonable suspicion must be based on articulable facts. Also, the officer’s belief that there is reasonable suspicion must be objectively reasonable, as later determined by a judge. There are instances where a detention exceeds the reasonable boundaries of an investigatory stop so as to constitute an arrest. At that point, probable cause is required for the arrest to be legal. Many times, an officer’s reasonable suspicion may evolve into probable cause, allowing the officer to make an arrest.